Adafruit 2.8 PiTFT - Capacitive Touch - Adafruit Learning System

Adafruit 2.8" PiTFT - Capacitive Touch
Created by lady ada
Last updated on 2014-10-07 10:45:13 AM EDT
Guide Contents
Guide Contents
2
Overview
3
Assembly
8
Easy Install
9
Ready to go image
9
DIY Installer script
9
Detailed Installation
15
Before you start
15
Download & Install
15
Module Auto-loading
18
Capacitive Touchscreen
25
Event Testing
26
TSLIB calibration
28
X11 Calibration
29
Using the Console
31
Backlight Control
32
Playing Videos
34
Displaying Images
35
Extras!
36
Tactile switch as power button
36
Making it easier to click icons in X
37
Gesture Input
40
F.A.Q.
41
Downloads
42
Schematic and Layout
42
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Overview
Our best-selling PiTFT just got a fancy upgrade, now we have a version with a capacitive
to uchscreen! That's right, instead of a resistive touchscreen, which requires a fingernail or
stylus, you can now use a fingerpad. The screen looks much nicer, with a black bezel and
glass overlay.
Featuring a 2.8" display with 320x240 16-bit color pixels and a capacitive touch overlay. The
plate uses the high speed SPI interface on the Pi and can use the mini display as a console, X
window port, displaying images or video etc. Best of all it plugs right in on top!
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Uses the hardware I2C Pins (SDA & SCL), SPI pins (SCK, MOSI, MISO, CE0) as well as GPIO #25
and #24. All other GPIO are unused. Since we had a tiny bit of space, there's 4 spots for
optional slim tactile switches wired to four GPIOs, that you can use if you want to make a
basic user interface. For example, you can use one as a power on/off button. See below for
the link to get the optional tact switches, they're not included.
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The screen is the same size as the resistive type so you can use this with the PiTFT PiBow or
any other enclosure you may already have. We also use the same SDL device and signals so
PyGame and X11 based programs can be swapped in with no changes in code.
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It's designed to fit nicely onto the Pi Model A or B rev 2 but also works perfectly fine with the
Model B+ as long as you don't mind the PCB overhangs the USB ports by 5mm, see the
photos above. Model B rev 1 have an older layout for the I2C pins and won't be able to use
the touch screen
This version comes as a mini-kit, with a 2x13 extra-tall female header (to connect the plate
to the Pi) and a 2x13 male header that can be used to connect an IDC cable or cobbler from
the side. The photos above also show the optional installed slim tactile buttons. The tactile
buttons are not included, but you can pick up a pack of 20 here. (http://adafru.it/1489) Some
basic soldering is required to install the headers. You can also pick up an extra-long Pi
stacking header if you want to install that instead of the 2x13 female header
installed. (http://adafru.it/1112)
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Assembly
This section is identical to the PiTFT Resistive 2.8" so please visit that page to complete
assembly of this Pi Plate
Visit the 2.8" Resistive PiTFT
Assembly Page
http://adafru.it/dDQ
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Easy Install
The PiTFT requires kernel support and a couple other things to make it a nice stand-alone
display. We have a detailed step-by-step setup for hackers who want to tweak, customize
or understand the PiTFT setup. If you just want to get going, check out the following for
easy-install instructions!
Ready to go image
If you want to start with a fresh image, we have one for Raspbian - click here to download it
and install into a new SD card. Unzip and follow the classic SD card burning tutorials
(http://adafru.it/aMW)
Download 2.8" Capacitive
Raspbian Image (2014/09/18)
http://adafru.it/e11
This image is customized for the CAPACITIVE touch 2.8" TFT, also known as PID #1983!
Not for PID #1601
Older images:
Raspbian 2014/06/20-based image (http://adafru.it/dSO)
DIY Installer script
If you don't want to download an image, you can run this script from inside your existing
Raspbian install. It will download the kernel add-ons, and configure your Pi for PiTFT joy
The script is available for perusal here (http://adafru.it/dSN)
you can download it with:
wget http://adafru.it/pitftsh
mv pitftsh pitft.sh
chmod +x pitft.sh
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Then run it with:
sudo ./pitft.sh -t 28c -r
This will install the "2.8 Capacitive" type of PiTFT into the current install.
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At the end you will be prompted on whether you want the text console to appear on the
PiTFT. Answer Y or N depending on your personal desires!
You will also be prompted on whether you want one of the tactile buttons to act as an 'on off'
switch. Answer Y or N depending on your personal desires!
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Thats it!
Run sudo rebo o t to try out your fancy new PiTFT :)
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Detailed Installation
If you've grabbed our Easy Install image, or use the script, this step is not required, it's
already done! This is just for advanced users who are curious on how to configure and
customize the kernel install
In the next few steps we'll cover the detailed installation procedure. Chances are, you
should grab the Easy Install image or script. If you have some interest in the details of how
we install the PiTFT setup, read on!
In order to add support for the 2.8" TFT and capacitive touchscreen, we'll need to install a
new Linux Kernel. Lucky for you, we created a kernel package that you can simply install
over your current Raspbian (or Raspbian-derived) install instead of needing a whole new
image. This makes it easier to keep your install up-to-date.
To use our kernel .deb files you must be using Raspbian or derivative. This wont work with
Arch or other Linux flavors. As Raspbian is the official OS for the Pi, that's the only Linux we
will support! Others can recompile their own kernel using our patchfile (http://adafru.it/cY2),
but we have no tutorial or support or plans for such.
Before you start
You'll need a working install of Raspbian with network access. If you need help getting that
far, check out our collection of Pi tutorials (http://adafru.it/aWq).
We'll be doing this from a console cable connection, but you can just as easily do it from the
direct HDMI/TV console or by SSH'ing in. Whatever gets you to a shell will work!
Also, run sudo apt-get update !
To run these all the setup and config commands you'll need to be logged into a proper
Terminal - use ssh, a console cable, or the main text console (on a TV). The WebIDE
console may not work.
Download & Install
Download the multiple files you'll need by running the following commands
cd ~
wget http://adafruit-download.s3.amazonaws.com/libraspberrypi-bin-adafruit.deb
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wget http://adafruit-download.s3.amazonaws.com/libraspberrypi-dev-adafruit.deb
wget http://adafruit-download.s3.amazonaws.com/libraspberrypi-doc-adafruit.deb
wget http://adafruit-download.s3.amazonaws.com/libraspberrypi0-adafruit.deb
wget http://adafruit-download.s3.amazonaws.com/raspberrypi-bootloader-adafruit-20140917-1.deb
Next install the new kernel with
sudo dpkg -i -B *.deb
This will take a few minutes so go make a sandwich or coffee
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If you have a version of Raspbian more recent than Sept. 2013, you'll need to turn off
the accelerated X framebuffer here, run "sudo mv /usr/share/X11/xorg.conf.d/99fbturbo.conf ~" to remove the accelerated X buffer and save it in your home directory
Now we'll just reboot to let it all sink in.
sudo shutdo wn -h no w (if you don't have the TFT installed, shutdown, place the
TFT on the Pi and re-power)
or
sudo rebo o t (if you have the TFT plate installed already)
Now that you're rebooted, log back in on the console/TV/SSH. There's no screen yet, we'll
do a test to make sure everything is perfect first!
Run the following commands to install the screen driver. Note that the screen will go from
white to black indicating the commands succeeded.
sudo mo dpro be spi-bcm2708
sudo mo dpro be i2c-bcm2708
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sudo mo dpro be fbtft_device name=adafruitct28 ro tate=90
Then you can do a quick graphics demo by starting up X11
sudo mv /usr/share/X11/xo rg.co nf.d/99-fbturbo .co nf ~
expo rt FRAMEBUFFER=/dev/fb1
startx
You should see the Pi desktop show up on the TFT! Congrats, you've completed the first
test perfectly. Now we'll make the TFT kernel modules automatically install on boot.
Hit Control-C in the console to quit the X server so we can continue configuration
Module Auto-loading
We'll now make the modules auto-load. Lets edit the /etc/modules list with
sudo nano /etc/mo dules
add two lines
i2c-bcm2708
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spi-bcm2708
fbtft_device
Then Co ntro l-X Y [return] to save
You're not done yet! Now we have to add the configuration details in a new modprobe file:
sudo nano /etc/mo dpro be.d/adafruit.co nf
add the following line
o ptio ns fbtft_device name=adafruitct28 ro tate=90
frequency=32000000
and save like you did before.
The ro tate= variable tells the driver to rotate the screen 0 90 180 or 270 degrees.
0 is portrait, with the bottom near the "Adafruit Logo"
90 is landscape, with the bottom of the screen near the buttons.
180 is portrait, with the top near the "Adafruit Logo"
270 is landscape, with the top of the screen near the buttons.
You can change this file with nano and reboot to make the change stick.
The frequency= variable tells the driver how to fast to drive the display. 32MHz
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(32000000) is a pretty nice 20 FPS rate but if your screen is acting funny, try taking it down
to 16MHz (16000000)
sudo rebo o t and look at the console output (or run dmesg in the console window after
logging in) you will see the modules install. Look in particular for the FT6X06 detection and
the ILI9340 screen frequency as highlighted here
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We can set up the touchscreen for ro tate=90 configuration by doing the following (for
more delicate calibration or for other rotate=XX values, see the next section)
Create the directory and new calibration configuration file:
sudo mkdir /etc/X11/xo rg.co nf.d
sudo nano /etc/X11/xo rg.co nf.d/99-capto uch.co nf
and enter in the following lines, then save.
Section "InputClass"
Identifier "captouch"
MatchProduct "ft6x06_ts"
Option "SwapAxes" "1"
Option "InvertY" "1"
Option "Calibration" "0 320 0 240"
EndSection
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You can now try to run X again with
FRAMEBUFFER=/dev/fb1 startx
The touchscreen now works, you can try it out!
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Type Control-C to quit X
If you don't ever want to have to type FRAMEBUFFER=/dev/fb1 before startx, you can make
it a default state by editing your profile file: sudo nano ~/.pro file and adding
expo rt FRAMEBUFFER=/dev/fb1
near the top and saving the file. Then reboot to reload the profile file. It will now always
assume you want to use /dev/fb1
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Capacitive Touchscreen
If you've grabbed our Easy Install image, or use the script, this step is not required, it's
already done! This is just for advanced users who are curious on how to configure and
customize the touchscreen
The nifty thing about capacitive touch screens is that they do no t require calibratio n!
The calibration is done 'in chip' on the screen itself. However, we still do need to tell the Pi
how to read the capacitive chip.
Before we start, we'll make a udev rule for the touchscreen. That's because the eventX
name of the device will change a lot and its annoying to figure out what its called depending
on whether you have a keyboard or other mouse installed.
Run
sudo nano /etc/udev/rules.d/95-ft6206.rules
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to create a new udev file and copy & paste the following line in:
SUBSYSTEM=="input", ATTRS{name}=="ft6x06_ts",
ENV{DEVNAME}=="*event*", SYMLINK+="input/to uchscreen"
Remove and re-install the touchscreen with
sudo rmmo d ft6x06_ts; sudo mo dpro be ft6x06_ts
Then type ls -l /dev/input/to uchscreen
It should point to eventX where X is some number, that number will be different on different
setups since other keyboards/mice/USB devices will take up an event slot
(http://adafru.it/dIX)
Event Testing
Even though capacitive touch screens don't require calibration, there are some useful tools
we can use to debug the touchscreen. Install the "event test" and "touchscreen library"
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packages with
sudo apt-get install evtest tslib libts-bin
Now you can use some tools such as sudo evtest /dev/input/to uchscreen which will
let you see touchscreen events in real time, press on the touchscreen to see the reports.
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TSLIB calibration
In order to use TSLIB - basically, the touchscreen without X11 - you'll need to set the
calibration for TSLIB in /etc/pointercal
With a resistive touchscreen, you have to calibrate it. Since capacitive touchscreens don't
require calibration you can just input the numbers directly. Run
sudo nano /etc/pointercal
And enter in the following values (there's a single space between each number) and hit
return afterwards. Then save
320 65536 0 -65536 0 15728640 65536
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Next you can run sudo TSLIB_FBDEVICE=/dev/fb1
TSLIB_TSDEVICE=/dev/input/to uchscreen ts_test
X11 Calibration
We can also manually enter in the touch calibration
edit the file with
sudo nano /etc/X11/xorg.conf.d/90-captouch.conf
and put the following in for rotation=90. For other rotations you may have to tweak
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SwapAxes and InvertY or InvertX
Section "InputClass"
Identifier "captouch"
MatchProduct "ft6x06_ts"
Option "SwapAxes" "1"
Option "InvertY" "1"
Option "Calibration" "0 320 0 240"
EndSection
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Using the Console
If you've grabbed our Easy Install image, or use the script, this step is not required, it's
already done! This is just for advanced users who are curious on how to configure and
customize the console
This section is identical to the PiTFT Resistive 2.8" so please visit that page to use the
console of this Pi Plate
Visit the Resistive 2.8" PiTFT
tutorial on using the Console
http://adafru.it/dIZ
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Backlight Control
Unlike the resistive PiTFT, the capacitive version does not have a resistive touch controller
chip that we can take advantage of as an extra backlight control pin. Instead, you can set up
GPIO #18 as an on/off or PWM control.
Note that if you are playing audio out the headphone jack, you can't use the PWM capabilities
of GPIO #18 at the same time, the PWM function is reassigned to do audio. However, you
can use it as a simple on/off pin
To enable using GPIO #18 as a backlight, so lder clo sed the #18 backlight
jumper o n the PiTFT capacitive PCB!
OK now you can use the PWM output on GPIO 18. There's python code available for
controlling the PWM but you can also just use the kernel module and shell commands.
With these basic shell commands, you can set the GPIO #18 pin to PWM mode, set the
frequency to 1KHz (1000 Hz) and set the duty cycle to 50:
echo
echo
echo
echo
pwm > /sys/class/rpi-pwm/pwm0/mode
1000 > /sys/class/rpi-pwm/pwm0/frequency
50 > /sys/class/rpi-pwm/pwm0/duty
90 > /sys/class/rpi-pwm/pwm0/duty
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Try other numbers, from 1 (off) to 99 (all the way on)!
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Playing Videos
This section is identical to the PiTFT Resistive 2.8" so please visit that page to play videos of
this Pi Plate
Visit the 2.8" resistive PiTFT
video-playing tutorial
http://adafru.it/dIY
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Displaying Images
This section is identical to the PiTFT Resistive 2.8" so please visit that page to display
images on this Pi Plate
Visit the 2.8" Resistive PiTFT
page on displaying images
http://adafru.it/dJ0
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Extras!
Tactile switch as power button
Its a good idea to safely turn off your Pi with a good sudo shutdo wn -h no w but that
often means pulling out a keyboard or connecting to the console. With our kernel we added
a cool module that will let you turn any GPIO into a power button. Since there's a couple of
tactile switches right there on the front, lets turn one into a power button. Press once to
properly turn off the pi, press again to start it up. Isn't that nice?
We'll be using GPIO #23, the left-most button. You can use any of them or other GPIO but
#23's our favorite number anyways.
You will have to grab a pack of slim tactile switches (http://adafru.it/1489) or otherwise
solder in a button
Add rpi_po wer_switch to /etc/mo dules and save
Now create a new conf file or edit our existing one with
sudo nano /etc/mo dpro be.d/adafruit.co nf
and enter in the line
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o ptio ns rpi_po wer_switch gpio _pin=23 mo de=0
Of course, change the gpio _pin setting to some other # if you wish. mo de=0 means its a
pushbutton not a switch. If you happen to install an on/off switch, use mo de=1
To make it active immediately run sudo mo dpro be rpi_po wer_switch
and short the two pads of the GPIO #23 button
Making it easier to click icons in X
If you want to double-click on icons to launch something in X you may find it annoying to get
it to work right. In LXDE you can simply set it up so that you only need to single click instead
of double.
From LXDE launch the file manager (sorry these pix are grayscale, still figuring out how to
screenshot the framebuffer!)
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Then under the Edit menu, select Preferences
Then select Open files with single click and close the window (you'll need to drag it
over to get to the X button
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Gesture Input
This section is identical to the PiTFT Resistive 2.8" so please visit that page to try out
gesture input on this Pi Plate
Visit the 2.8" Resistive PiTFT
Gesture Input page
http://adafru.it/dJ1
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F.A.Q.
The display works, but the capacitive touch part doesnt
Check that you installed the right image, there's one for resistive and one for capacitive
PiTFT's
If that doesn't help, you can verify your RasPi model number with the command cat
/pro c/cpuinfo , if it's revision # 0002 or 0003 that means it's a rev 1 Model
B, (http://adafru.it/dXg) and will not work due to the I2C pins changing.
Does this screen do multi-touch?
Nope! This capacitive touch screen is single-touch only.
Hey...I was looking at the FT6206 datasheet and it looks like it can support multitouch (two
points)!
The chip does in fact support multitouch, but the screen layout itself is single-touch.
We'll keep looking for a low cost multitouch screen, but we found that at the small size of
this screen, single-touch is pretty good! Also, very few linux programs support MT.
How do I automatically boot to X windows on the PiTFT?
Check out the 2.8" resistive PiTFT FAQ (http://adafru.it/e1o) for an answer to this common
question.
I have some more questions!
Check out the 2.8" Resistive PiTFT FAQ page for some other questions you may want
answered
Visit the 2.8" Resistive PiTFT
FAQ page
http://adafru.it/dJ2
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Downloads
The latest kernel fork that adds all the TFT, touchscreen, and other addons is here on
github (http://adafru.it/dcA)
Datasheet for the 'raw' 2.8" TFT display (http://adafru.it/d4m)
FT6206 Datasheet (http://adafru.it/dRm) & App note (http://adafru.it/dRn) (capacitive
chip)
Schematic and Layout
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В© Adafruit Industries
Last Updated: 2014-10-07 10:45:15 AM EDT
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